The goal of our proposal is to define a mechanism by which commonly employed anesthetic agents and major surgical procedures can enhance the growth of a malignant tumor. Our hypothesis is that certain anesthetic agents alone and other anesthetic agents in combination with surgery impair host immunity and can result in an increase in tumor growth. Preliminary data is presented to support this hypothesis. Mice develop an increase in pulmonary metastase from Thiopental alone or major surgical procedure. An immunorestorative drug, Thiabendazole, given in the perioperative period can decrease the number of pulmonary metastases. The experimental plan is based upon the delayed-type hypersensitivity response to DNCB of mice, both normal and tumor-bearing, following surgery and anesthesia. This assay will be used to determine whether the defect is in the afferent or efferent arm of the immune response. Subsequently, specific in vitro assays of afferent or efferent responses will be used to localize the immune cell population(s) or interaction(s) responsible for the immunosuppression. Finally, an attempt will be made to specifically reconstitute anesthesia/surgery treated tumor-bearing mice with cells from mice treated with an immunorestorative agent, Thiabendazole. Efficacy of this approach will be determined by decreases in metastatic tumor growth and restoration of immune reactivity.